Answer:
[tex]\Sigma\left {n} \atop {1}} \right. (5n^2+3n)[/tex]
Step-by-step explanation:
Given the series 8 + 18 + 28 + 38
First, we need to find the sum of the nth term of the sequence as shown
Sn = n/2[2a+(n-1)d]
n is the number of terms
a is the first term = 8
d is the common difference = 18-8 = 28-18 = 10
Substitute
Sn = n/2 [2(8)+(n-1)*10]
Sn = n/2 [16+10n-10]
Sn = n/2[10n+6]
Sn = 2n/2(5n+3)
Sn = n(5n+3)
Sn = 5n²+3n
In Sigma form;
[tex]\Sigma\left {n} \atop {1}} \right. (5n^2+3n)[/tex]
